The present invention relates to attaching a wire to the shell of a base on an electric lamp and, more particularly, to an assembly that enables the wire to be welded to the base in a way that prevents undesirable movement of the base relative to the lamp.
The present invention relates generally to assembly of an electric lamp (i.e., a light bulb which is known in the art as a xe2x80x9clampxe2x80x9dxe2x80x94the xe2x80x9cbulbxe2x80x9d is only the outer glass envelope). In particular, the invention concerns both a means for attaching a wire to the shell of a base on the lamp, and also to a means of securing the base on the lamp. Typically, the base is attached to the neck of a xe2x80x9csealed lampxe2x80x9d wherein one of the electrical xe2x80x9clead wiresxe2x80x9d (a sidewire) is trapped between the bulb neck and the base, and then the sidewire is electrically connected to the side of the base. Historically, the electrical attachment is by means of soldering, but there is now a big push to avoid the use of lead (a primary component in most solders) for environmental reasons. Lamp makers have implemented various means for welding the sidewire instead of soldering, but there are many problems associated with sidewire welding. For example, heat generated in the welding process can cause damage to the glass bulb that may lead to premature lamp failure. Also, the average weld quality and amount of variation in the weld quality depend on the materials used in the welded parts, the dimensions of the welded parts, the positioning of the welded parts, and many other factors known in the welding arts.
A further set of problems is raised when sidewire welding is substituted for soldering in lamps that involve high temperature use, for example in lamps generally known as High Intensity Discharge (HID) lamps. Because of high lamp operating temperatures, basing cement is typically not used to secure the base onto the bulb; rather screw threads can be formed in the glass neck of the bulb (forming a xe2x80x9cthreaded sealxe2x80x9d) upon which the base can be screwed onto the lamp. This is a well known process in the lamp making industry. Typically, a vertical groove is formed across the screw threads in the glass neck to provide a recess for the sidewire to lie in. Once the base is screwed on, the groove can be filled with molten solder to electrically attach the wire (in the groove) to the base shell where it passes over the groove. Once it hardens, the solder serves a desired additional purpose of locking the base in position so that it cannot be unscrewed off of the lamp. If the solder fills the groove properly, the base will not be able to move more than a degree or so relative to the bulb, and many lamp applications specify very tight limits on such movement. As a result, regulatory agencies such as ANSI (American National Standards Institute) and IEC (International Electrotechnical Commission) have published standards that require no more than a small number of degrees movement of the base relative to the bulb. When solder is replaced by welding for such lamps, new ways of securing the base to the bulb must be developed.
U.S. Pat. No. 6,346,767 (Swadel, et al.; 2002)xe2x80x94xe2x80x9cSwadelxe2x80x9dxe2x80x94discloses a lamp with a formed, cemented clip to secure base to lamp. The lamp""s bottom portion (21) has threads (23) and a groove (25) ending in a deeper cavity (receiving port 25a). The side lead-in wire (34) is attached, as by welding, to a locking clip (10), and the wire-clip assembly lies in the groove such that a scyphate middle portion (16) of the clip is accepted by the receiving port. The base (32) is threaded onto the bottom threads (23) and an end portion (18) of the locking clip is welded to the base by bending the end portion over the top of the base in order to contact the outside surface of the base. An adhesive chemical attachment means (50) is located in the receiving port (25a) to chemically affix the locking clip (10) to the lamp end (21).
U.S. Pat. No. 5,032,759 (Thiry, et al.; 1991)xe2x80x94xe2x80x9cThiryxe2x80x9dxe2x80x94discloses a lamp base (10) comprising a metal shell contact (14) containing a molded glass body (12) that has a cylindrical wall (18). The invention comprises thinning the wall (18) in an area behind the point (a weld zone 48) where a side lead (50) is to be welded to the exterior surface of the shell contact (14). The thinning is intended to deter slumping of the glass adjacent the weld zone. Thiry teaches (column 1, lines 34-49) that the existence of a gap between the glass and the shell causes welding problems due to allowed flexing of the shell when the lead is pressed against the shell by the welding tool. The welding problems are said to result in occurrences of weld failure in two to five percent of lamp production involving the subject type of base.
The Swadel patent avoids the use of solder, but does not address situations where high operating temperatures may negate the effectiveness of the adhesive used to secure the base to the lamp. The Thiry patent discloses problems that arise when resistance welding a wire to a base shell when there is a cavity with insufficient support for the shell. It is an objective of the present invention to solve these and other problems that arise when both electrically connecting a sidewire to a base and also securing the base to a lamp without using either solder or adhesive.
According to the invention, a lamp assembly comprises a metal screw base having base screw threads; an outer jacket having a threaded seal wherein seal screw threads are formed in a neck portion of the outer jacket, such that the seal screw threads conform to the base screw threads to allow the base to be screwed onto the threaded seal; one or more lead wires extending out of a bottom of the threaded seal; a flag assembly comprising a wire in a close-fitted electrically nonconductive sleeve, the flag assembly having an outer end comprising a flag; a groove formed across the seal screw threads and dimensioned to closely fit around the flag assembly; and the flag assembly being positioned in the groove such that an inner end of the flag assembly is electrically connected to at least one of the one or more lead wires, and the flag of the flag assembly is bent over a lip of the screw base and welded to an outside surface of the screw base.
Further according to the invention, the lamp assembly is such that the wire of the flag assembly is at least one of the one or more lead wires.
Further according to the invention, the lamp assembly is such that the inner end of the flag assembly is electrically connected to at least one of the one or more lead wires by welding.
Further according to the invention, the lamp assembly is such that the flag comprises flat metal. Preferably, the flag is a separate piece of flat metal stock that is electrically and mechanically connected to the wire; and a shank portion of the flag assembly where the flat metal stock overlaps the wire is conformed to the shape of the wire and is covered by the sleeve. More preferably, the flag has a thickened portion that is positioned in the vicinity of a fold where the flag assembly is bent over the lip of the screw base; and the thickened portion traversingly extends to at least one of two lateral edges of the flag. Most preferably, the thickened portion comprises an extended end of the wire that is formed such that the extended end traverses a flat side of the flag. Further, the thickened portion extends under the sleeve enough to increase the magnitude of a sleeve covered flag thickness; and the thickened portion extends out to the fold such that the fold is able to bend around the outer end of the thickened portion.
Further according to the invention, the lamp assembly is such that the flag assembly is welded to the outside surface of the screw base by means of resistance welding.
Further according to the invention, the lamp assembly is such that the sleeve comprises a resilient, high temperature material.
According to the invention, a method for securing a base on a lamp comprises the steps of:
a) forming seal screw threads in a neck portion of the lamp such that the seal screw threads conform to base screw threads of the base;
b) providing a flag assembly comprising a wire in a close-fitted electrically nonconductive sleeve, the flag assembly having an outer end comprising a flag;
c) forming a groove across the seal screw threads wherein the groove is dimensioned to closely fit around the flag assembly;
d) positioning the flag assembly in the groove;
e) screwing the base onto the seal screw threads;
f) bending the flag over a lip of the base; and
g) welding the flag to an outside surface of the base.
According to the invention, the method further comprises the steps of: providing a flat metal portion for the flag, wherein at least a part of the flat metal portion is covered by the sleeve; providing the flat metal portion by electrically and mechanically connecting a piece of flat metal stock to the wire; for a shank portion of the flag assembly where the flat metal stock overlaps the wire, conforming the flat metal stock to the shape of the wire and covering the shank portion by the sleeve; providing a thickened portion on the flag; providing the thickened portion by extending the wire; and forming an extended end on the wire such that the extended end traverses a flat side of the flag and extends to at least one of two lateral edges of the flag.
According to the invention, the method further comprises the step of using resistance welding to weld the flag to the outside surface of the base.
According to the invention, the method further comprises the steps of: electrically connecting at least one of one or more lead wires of the lamp to the base by electrically connecting an inner end of the flag assembly to at least one of the one or more lead wires; and utilizing at least one 30b of the one or more lead wires as the wire of the flag assembly.
According to the invention, the method is such that the groove comprises a flag recess connected to, and extending from, a wire channel; and the groove being dimensioned to closely fit around the flag assembly comprises at least the flag recess being dimensioned to closely fit around the flag. The method then further comprises the step of forming the groove across the seal screw threads wherein the groove is circumferentially located such that one external seal thread valley crosses the wire channel at a thread crossing location that is approximately in the center of a long dimension of the wire channel.
According to the invention, a flag assembly for an electric lamp, comprises: a wire in a close-fitted electrically nonconductive sleeve; an outer end comprising a flag, formed from flat metal stock that is electrically and mechanically connected to the wire; a shank portion where the flat metal stock overlaps the wire, is conformed to the shape of the wire, and is covered by the sleeve; and a thickened portion that is positioned in the vicinity of a fold that traverses the flag from one lateral flag edge to the other lateral edge.
Further according to the invention, the flag assembly is such that the thickened portion traversingly extends to at least one of the lateral edges of the flag. Preferably the thickened portion comprises an extended end of the wire that is formed such that the extended end traverses a flat side of the flag; the thickened portion extends under the sleeve enough to increase the magnitude of a sleeve covered flag thickness, and the thickened portion extends out to the fold such that the fold is able to bend around the outer end of the thickened portion.
Further according to the invention, the flag assembly is such that the wire is electrically connected to at least one of one or more lead wires of the lamp; and the flag is bent over a lip of a base of the lamp, and is welded to an outside surface of the base.
Further according to the invention, the flag assembly is such that the electrically nonconductive sleeve comprises a resilient, high temperature material; and the flat metal stock comprises nickel ribbon. Preferably the sleeve comprises PTFE shrink tubing.
Other objects, features and advantages of the invention will become apparent in light of the following description thereof.